Anthropogenic Hydrological Regulation Drives Carbon Pool Dynamics in the Alluvial Wetlands of the Lower Yellow River

ABSTRACT Alluvial wetlands are vital river components and crucial nodes of the carbon cycle, yet the response of their surface soil carbon pools to anthropogenically regulated hydrological rhythms is not fully understood. Surface soil samples were collected from the alluvial wetlands of the lower Yellow River (LYR) during three distinct hydrological seasons preceding and following a Water and Sediment Regulation Scheme (WSRS) event. The gradient acid hydrolysis method was used for carbon fractionation (labile carbon (LP‐C) and recalcitrant carbon (RP‐C) fractions) in soil, and water and soil physicochemical parameters were monitored to assess the effects of anthropogenic hydrological regulation on surface soil carbon content and stability within alluvial wetlands. Results indicated that total carbon and LP‐C concentrations in the alluvial wetland soil reached their highest levels during the WSRS‐imposed high‐flow periods, with 13.75 ± 2.47 g/kg and 7.34 ± 3.18 g/kg, respectively. Further correlation analysis indicated that alterations in hydrologic conditions under WSRS primarily influence the composition and stability of soil carbon by modulating suspended sediment (SS) input fluxes and soil environmental characteristics. In light of these findings, under the scenario of increasingly intense anthropogenic regulation of hydrological rhythms, enhancing SS deposition, restoring wetland vegetation, and reducing soil respiration represent potential pathways to improve carbon pool capacity in alluvial wetlands. This study highlights the important role of anthropogenic hydrological regulation in wetland carbon storage and cycling processes, providing valuable insights for the river carbon budget of regulated river systems under changing environments.